A sewerage inlet of this type is known from the Utility Model DE 93 11 176. The known sewerage inlet serves the drainage of heating cellars. It is provided with a permanently closed seal, which only opens when water runs in and remains closed, if fuel oil or another liquid which is lighter than water flows into the container.
This known sewerage inlet is unsuitable for the drainage of surface water on streets, grounds, production yards and the like because the container respectively the outflow housing has no storage volume and therefore would overflow already when running off small volumes of water and the float and the valve are arranged such in the discharge current that due to the turbulences occurring there a reliable closing of the valve upon influx of petrol, diesel oil or heating oil cannot be expected.
To protect the groundwater and the surface waters the arrangement of separators in the canalisation is known, in which light liquids such as petrol, benzol, oil or diesel are separated from water.
Despite these separators considerable damages occur frequently when, for example, in the case of a carambolage of a tanker convoy oil or petrol flow into a gully and from there via canalisation into the groundwater or streams or rivers. Here it is to be taken into consideration that the sewage pipes are frequently not joined together tightly and also are not connected tight to the inlet shaft of a gully.